1. Field of the Invention
The present invention relates to an electromagnetic clutch, and more specifically, to an electromagnetic clutch suitable for use in compressors.
2. Description of Related Art
An electromagnetic clutch is used as a power transmission for a compressor. For example, a known structure of a scroll-type compressor having an electromagnetic clutch is constructed as depicted in FIG. 17. In FIG. 17, electromagnetic clutch 100 is assembled around cylindrical projected portion 121a of front housing 121 of scroll-type compressor 120. Electromagnetic clutch 100 includes rotor 101, which is mounted upon projected portion 121a via bearing 123. Rotor 101 has inner cylindrical portion 101a, outer cylindrical portion 101b, and bottom portion 101c connecting the ends of cylindrical portions 101a and 101b. Containing space 101d is formed by portions 101a, 101b and 101c. Electromagnet device 102 is enclosed within containing space 101d of rotor 101.
Armature 103 is provided facing one end of rotor 101. Armature 103 is connected to stopper plate 105 via plate spring 104. Stopper plate 105 is fixed to boss portion 106 via rivets 107. Boss portion 106 is fixed to end portion 122a of drive shaft 122 by threaded nut 108.
In electromagnetic clutch 100, a rotational torque is transmitted from an external power source (not shown) to rotor 101 via a V belt (not shown). When electromagnet device 102 is not energized, because armature 103 is urged by plate spring 104 away from rotor 101, even if rotor 101 rotates, armature 103 does not rotate. Therefore, the rotational torque of rotor 101 is not transmitted to drive shaft 122. When electromagnet device 102 is energized, armature 103 is attracted to the end of rotor 101 by the attracting force generated by electromagnet device 102, in opposition to the urging force applied by plate spring 104. Therefore, rotor 101 and armature 103 are integrated, and rotated together. The rotational torque of rotor 101 is transmitted to drive shaft 122 through stopper plate 105 and boss portion 106, thereby driving compressor 120.
FIG. 18 depicts an inclined plate-type compressor as another type of compressor. In FIG. 18, electromagnetic clutch 110 is assembled around of cylindrical projected portion 131a of front housing 131 of inclined plate-type compressor 130. Electromagnetic clutch 110 may have a structure similar to that depicted in FIG. 17.
FIG. 19 depicts an example of the detailed structure of the electromagnet device depicted in FIG. 17 or 18. In FIG. 19, electromagnet device 102 has ring member 113 forming therein a containing chamber 113a. Ring-like plate 114 is provided on one end outer surface of ring member 113 for fixing ring member 113 on a front housing of a compressor. Coil bobbin 112 provided with coil element 111 is housed within containing chamber 113a of ring member 113. Coil bobbin 112 is enclosed within containing chamber 113a by charging resin 115, such as an epoxy resin into containing chamber 113a. Thus, in a known technology, a method for molding a resin is employed for preventing water or foreign material from entering into an electromagnetic clutch, including for ensuring the properties of vibration resistance, heat radiation resistance, and water proofing.
FIG. 20 depicts another example of the detailed structure of the electromagnet device depicted in FIG. 17 or 18. In FIG. 20, electromagnet device 102xe2x80x2 has bobbin 116 formed as two separate parts. After coil element 111 is enclosed within the two parts of bobbin 116, bobbin 116 is housed within containing chamber 113a of ring member 113. Enclosed bobbin 116 then is fixed by caulked portions 117 formed at the partial inner edges of the opening portion of containing chamber 113a. 
In the known structure depicted in FIG. 19, however, because resin 115 for molding generally is a thermosetting resin, such as an epoxy resin, manufacturing electromagnet device 102 requires an expensive furnace for curing of the resin. Further, it takes a long period of time to cure the resin, thereby decreasing the productivity of manufacturing processes for such an electromagnetic clutch.
In the known structure depicted in FIG. 20, it is difficult to completely prevent water from entering into coil element 111 through a gap between the two parts of bobbin 116. Therefore, there is a problem insulating coil element 111.
Accordingly, it is an object of the present invention to provide an improved structure for an electromagnetic clutch that may increase the productivity of manufacturing processes by stopping use of a molding resin, and that may ensure the proper insulation of an electromagnet device.
To achieve the foregoing and other objects, an electromagnetic clutch according to the present invention is provided. The electromagnetic clutch includes an electromagnet device housed within a rotor. The electromagnet device comprises a ring member having a containing chamber, a coil member housed within the containing chamber of the ring member. The coil member comprises a bobbin and a coil element provided within the bobbin. The electromagnet device comprises a seal mechanism provided for enclosing the coil element within the containing chamber of the ring member in a sealed-off condition.
In the electromagnetic clutch, the seal mechanism comprises a seal plate to improve the seal formed between the bobbin and the ring member. The seal plate engages an engaging portion formed on an inner surface of the containing chamber of the ring member. The seal plate may comprise a side plate portion integral with the bobbin. Alternatively, the seal plate may comprise a resin plate provided separately from the bobbin.
The engaging portion may comprise a first groove formed on the inner surface of the containing chamber of the ring member. The first groove extends circumferentially about the ring member. Further, the engaging portion may comprise a stepped portion formed on the inner surface of the containing chamber of the ring member. The stepped portion extends circumferentially about the ring member.
The seal plate may have a projection extending circumferentially about the ring member. The projection engages the engaging portion formed on the inner surface of the containing chamber of the ring member. The projection may be brought into contact with the engaging portion. Further, the projection may be fitted into a second groove formed on the engaging portion. The second groove extends circumferentially about the ring member.
Further, the seal plate may have a V-shaped groove on its radial end surface, i.e., a radially outer end surface, or a radially inner end surface, or both. The seal plate may have a notch on its edge portion. The notch extends circumferentially about the seal plate.
The seal plate is fixed in the containing chamber of the ring member. For example, a part of the inner surface of the containing chamber of the ring member is crimped, and the seal plate is fixed in the containing chamber of the ring member by the crimping. Crimping may include the formation of a wave, bulge, crinkle, warp, or similar deformation in the ring member surface. A plurality of crimped portions may be disposed circumferentially about the ring member, or a crimped portion may extend continuously over the entire circumference of the ring member. The crimped portion, or portions, may be disposed on the inner surface of an outer cylindrical portion of the ring member, or an outer surface of an inner cylindrical portion of the ring member, or both.
An inner surface of of the containing chamber of the ring member positioned below the engaging portion, may be formed as a tapered surface causing a width of the containing chamber to gradually decrease.
The seal mechanism may comprise a protruded portion placed into contact with an inner surface of the containing chamber of the ring member. The protruded portion extends circumferentially about the ring member. The cross-sectional shape may be rectangular, semi-circular, triangular, or trapezoidal.
Such an electromagnetic clutch is used, for example, for a compressor. Any type of the compressor may be available.
In the electromagnetic clutch according to the present invention, the seal mechanism does not require a molding resin to achieve a desired quality of seal. The number of manufacturing steps may be decreased by stopping use of the molding resin, thereby reducing the cost for the manufacture of the electromagnetic clutch.
Further, because the seal mechanism may achieve a high quality of seal for the coil element without using a molding resin, the proper insulation of the coil element may be ensured readily and less expensively.
Further objects, features, and advantages of the present invention will be understood from the following detailed description of preferred embodiments of the present invention with reference to the accompanying figures.